[util,otp] Make OTP Image MEM lines deterministic

Sorts the set of word annotations for a MEM line in the OTP image, such
that the MEM line being read by Vivado is the same, but the word
annotations always appear in the same order, making the builds
deterministic. Previously, usage of python's sets meant that for
MEM lines with multiple word attributes, they could appear in different
orders between builds, causing bitstream splice reruns where not
necessary.

Signed-off-by: Alex Jones <[email protected]>

util/design/lib/OtpMemImg.py

@@ -145,7 +145,7 @@ def _to_memfile_with_ecc(data, annotation, config,
         # count ECC bits. In a comment, we also include any annotations
         # associated with the word.
         line = '@{:06x} {} // {}'.format(i_word, word_hex,
-                                         ', '.join(word_annotations))
+                                         ', '.join(sorted(word_annotations)))
         mem_lines.append(line)
 
     log.info('Done.')